This application claims the benefit of Korean Application No. 2002-40667, filed Jul. 12, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a liquid image forming system, the structure of which is simplified using a high-concentration developing agent, and a method of forming an image using the same.
2. Description of the Related Art
In general, liquid image forming systems radiate light onto a photosensitive body, form an electrostatic latent image corresponding to a desired image on the photosensitive body, develop the electrostatic latent image with a developing agent in which toner in powder form is mixed with a liquid solvent, and then prints the image onto a piece of paper.
FIG. 1 shows the structure of a conventional liquid image forming system disclosed in U.S. Pat. No. 5,255,058.
As shown in FIG. 1, the conventional liquid image forming system includes a photosensitive body 10 charged to a predetermined potential by a charger 14, a light scanning unit (LSU) 16 which radiates light onto the charged photosensitive body 10, forms a relative potential difference thereon, and forms an electrostatic latent image corresponding to a desired image, a developing agent-supplying unit which supplies a developing agent to the photosensitive body 10 to form the electrostatic latent image, and a transfer body 30 which transfers the image developed on the photosensitive body 10 and prints the image onto a piece of paper 72.
In general, the developing agent-supplying unit prepares a developing agent with a toner concentration of less than 3% solid and supplies the developing agent between the photosensitive body 10 and a developing roller 38. To do this, the developing agent-supplying unit includes concentrated cartridges 82 and 84, in which a concentrated developing agent of about 25% solid is dipped, and a solvent cartridge 86 in which a pure solvent is stored. The development agent-supplying unit also includes mixing tanks 55, 57, 59, and 61 which mix the concentrated cartridges 82 and 84 with the solvent to prepare a developing agent with a uniform concentration of about 2-3% solid, a supplying unit 20 which pumps the developing agent prepared in the mixing tanks 55, 57, 59, and 61 to pumps 90, 92, 94, and 96 and supplies the developing agent to the developing roller 38, and a withdrawing unit which withdraws the developing agent remaining after a developing operation. The withdrawing unit includes a collecting container 50 which collects the developing agent flowing after being supplied between the developing roller 38 and the photosensitive body 10 and returns the collected developing agent to the mixing tanks 55, 57, 59, and 61 for each color, a squeeze roller 26 which presses the photosensitive body 10 on which an image is developed, and squeezes a solvent contained in the developed image, and a separator 66 which withdraws the squeezed developing agent from the collecting container 50, separates the toner from the developing agent, and returns a solvent to a solvent tank 65.
In the above structure, in order to perform a developing operation, developing agents having four colors such as yellow (Y), magenta (M), cyan (C), and black (K), with a uniform concentration of 2-3% solid, are prepared in each of the mixing tanks 55, 57, 59, and 61, respectively. Of course, only one developing agent is prepared in a system to perform a development operation using a single color such as a black-and-white image. However, a system in which four-color developing agents are prepared so as to implement color images is disclosed here. In order to prepare developing agents for each color, the developing agent-supplying unit supplies the concentrated developing agent and the pure solvent to the mixing tanks 55, 57, 59, and 61 from the concentrated cartridges 82 and 84 and the solvent cartridge 86, thereby manufacturing a developing agent with a predetermined concentration. For this purpose, in general, a concentration sensor (not shown) is provided in each of the mixing tanks 55, 57, 59, and 61 and measures the concentration of the mixed developing agent. In this way, if developing agents are prepared for each color, the developing operation begins. First, the charger 14 charges the photosensitive body 10 to a predetermined potential. In this state, the LSU 16 radiates light onto the charged photosensitive body 10, reduces a potential thereon, thereby forming an electrostatic latent image corresponding to a desired image. Subsequently, the pumps 90, 92, 94, and 96 operate and supply the developing agents prepared in the mixing tanks 55, 57, 59, and 61 between the developing roller 38 and the photosensitive body 10 via the supplying unit 20, thereby developing the electrostatic latent image. The developed image is transferred onto the transfer body 30. If the image is an image formed of one color, the image is directly printed on the paper 72. However, if a color image is implemented with a plurality of overlapped color developing agents, an image developed for each color is overlapped on the transfer body 30 by repeating charge, exposure, and development operations for four colors such as yellow (Y), magenta (M), cyan (C), and black (K). The overlapped color image is printed on the paper 72 passing between the transfer roller 30 and a compressing roller 71.
However, as described above, the structure of the liquid image forming system requiring the operations of preparing, supplying, and withdrawing the developing agent, is very complicated. This is because a concentrated high-concentration developing agent cannot be used, but instead a low-concentration developing agent of less than 3% solid is used during the developing operation. Of course, if the developing agent is manufactured with a low-concentration and is used during the developing operation, mobility is improved, and a difference in toner density for each portion of the developed image is reduced. However, as described above, the conventional liquid image forming system requires a very complicated structure. Specifically, the concentrated developing agent and the solvent are dipped in the concentrated cartridges 82 and 84 and the solvent cartridge 86, respectively, are transferred to the mixing tanks 55, 57, 59, and 61, and are mixed with a low-concentration developing agent of less than 3% solid for development to thereby form an electrostatic latent image. Then, the solvent contained in the developed image is squeezed and withdrawn to be in a high-concentration state suitable for printing. Thus, the size of the liquid image forming system or costs are increased.
In addition, since a transfer operation of an image formed of a low-concentration developing agent is performed, even after a squeezing operation is completed, liquid may easily flow out due to a pressure applied during the transfer operation. Thus, it is quite possible that an image may be spread or dragged. Accordingly, in order to obtain a clear image, the transfer roller 30 should have a special structure having a humidity-absorption layer. Also, an additional image-drying apparatus, which prevents the image from spreading during the transfer operation by drying an image, should be further provided. Also, if the image-drying apparatus is installed, the temperature in a printer is greatly increased. Thus, in order to prevent deterioration of the performance of the photosensitive body 10, a cooler should be further installed.
Hence, a new liquid image forming system that can solve the above problems is required.
Accordingly, it is an aspect of the present invention to provide a liquid image forming system having an improved structure, in which a high-concentration developing agent is used without requiring a squeezing operation during a developing operation, and a method of forming an image using the same.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
The foregoing and/or other aspects of the present invention are achieved by providing a liquid image forming system including a photosensitive body on which an electrostatic latent image is formed; a developing roller which forms a contact nip with the photosensitive body and develops the electrostatic latent image with a developing agent having a color; a metering member which is closely adhered to the developing roller and regulates the developing agent on the developing roller to a predetermined thickness; an intermediate transfer medium onto which the image formed on the photosensitive body is transferred via a first transfer nip formed therebetween; and a transfer roller, which forms a second transfer nip with the intermediate transfer medium, and transfers the transferred image onto a printing medium passing between the intermediate transfer medium and the second transfer nip, wherein a pressure applied to the contact nip is less than 1.2 times a pressure of the metering member on the developing roller, a pressure applied to the first transfer nip is less than 1.2 times the pressure applied to the contact nip, and a pressure applied to the second transfer nip is less than 1.5 times the pressure applied to the first transfer nip.
The foregoing and/or other aspects are achieved by providing a method of forming a liquid image. The method includes forming an electrostatic latent image on a photosensitive body; staining a developing agent on a developing roller which forms a contact nip with the photosensitive body; regulating the developing agent to a thickness using a metering blade closely adhered to the developing roller; developing the electrostatic latent image while maintaining a pressure applied to the contact nip to be less than 1.2 times a pressure of the metering blade on the developing roller; transferring the developed image onto an intermediate transfer medium which forms a first transfer nip with the photosensitive body, while maintaining a pressure applied to the first transfer nip to be less than 1.2 times the pressure applied to the contact nip; and transferring the transferred image from the intermediate transfer medium onto a printing medium passing between the intermediate transfer medium and a transfer roller, while maintaining a pressure applied to a second transfer nip between the intermediate transfer medium and the transfer roller to be less than 1.5 times the pressure applied to the first transfer nip.